The invention relates to filters, particularly extended life filters, and further particularly to combinations separating filtering and storage functions.
End users are seeking to extend the service intervals and reduce service for various machines requiring filtering of a working fluid, such as lubricating oil for internal combustion engines, hydraulic fluid for hydraulic equipment, and the like. Ultimately, the user would like to have service-free equipment. For a variety of reasons, this goal has not been attained. One of the reasons is the requirement for filters, such as lube, hydraulic and fuel filters, to be serviced periodically. In the case of conventional disposable filters, the filters do not have great enough contaminant-holding capacity to last the life of the equipment. In the case of cleanable filters, capacity is not an issue, if the filter is cleaned on a regular basis, but rather the contaminant removed from the filter must be disposed of somehow. One possible solution in an internal combustion engine is to burn the contaminant with the fuel, for example as shown in commonly owned copending U.S. application Ser. No. 09/210,363, filed Dec. 11, 1998, now U.S. Pat. No. 6,273,031, incorporated herein by reference. The present invention provides another solution.
In one aspect of the present invention, a cleanable backwashable filter, for example as shown in U.S. Pat. Nos. 5,462,679, 5,779,900, 5,858,224, and commonly owned copending U.S. application Ser. Nos. 09/210,363, filed Dec. 11, 1998, now U.S. Pat. No. 6,273,031, 09/563,737, filed May 3, 2000, now U.S. Pat. No. 6,378,706, and 09/466,388, filed Dec. 17, 1999, now U.S. Pat. No. 6,319,402 incorporated herein by reference, is provided in combination with a contaminant separator receiving and filtering the contaminant-laden working fluid backwashed from the cleanable filter. The contaminant separator separates contaminant from the working fluid, and also stores the contaminant. In one aspect, the fluid after separation of contaminant is returned to the circulation system circulating working fluid to the machine, thus providing in combination with the cleanable filter a permanent filter system, or at least a reduced-service filter system. The contaminant separator is preferably a batch processor operative during the backwash mode of the cleanable filter and receiving contaminant-laden working fluid from the cleanable filter and separating and storing contaminants, and passing working fluid.
The cleanable main filter is a continuous flow filter in the filtering mode, and, in one aspect, the batch processor contaminant separator is a noncontinuous flow centrifuge having a rotor driven during the backwash mode of the cleanable main filter, and nondriven during the filtering mode of the cleanable main filter. In a desirable aspect, when air is used as the cleansing fluid for the cleanable filter, the same source of compressed air may be used to drive a turbine on the centrifuge rotor. The backwashed contaminant-laden fluid from the cleanable filter is discharged to the centrifuge, whose rotor is preferably already spinning or rapidly speeding up, causing the fluid to form a hollow cylindrical air core due to centrifugal force, which central air core allows excess purge air to escape from the rotor even though full of purge fluid such as lubricating oil. Other sources of motive force may be used for the centrifuge, though pressurized air is preferred for simplicity if already used for backwashing the main cleanable filter.
The centrifuge is sized to hold at least one housing-full of fluid of the cleanable filter in addition to a desired quantity of packed contaminant such as sludge for intended centrifuge service intervals, i.e. a rotor that is full of separated contaminant or sludge must still have enough residual volume to hold one filter-full of fluid or oil from the main cleanable filter. Following the purge cycle of the cleanable filter, the centrifuge is driven for a sufficient length of time to separate the desired contaminants from the fluid, for example in engine oil applications, the length of such time is a function of the centrifuge geometry, speed and oil viscosity, with typically a 1 to 5 minute interval being adequate to remove particles greater than 1 micron. After this interval, the air supply to the rotor turbine is discontinued, and the rotor gradually comes to a stop. The clean separated fluid then drains out of the rotor by gravity, and preferably drains by gravity back to an engine oil sump in such application. Alternatively, the drain back to the sump can be assisted by a delayed charge of compressed air pressurizing the centrifuge housing and forcing the oil through the drain line back to the oil reservoir or sump, thus enabling use of a small diameter drain line and avoiding problems with hydraulic trap or a below-oil drain entry port on the sump.
Separated contaminants such as sludge remain in the centrifuge housing, forming a cylindrical cake, with loose or nonadhesive particles trapped preferably in a storage chamber in the rotor preferably filled with high-loft filter media preferably comprising a matrix of filter material of at least 75% void volume, preferably at least 95%. In a further aspect, this desirably reduces fluid turbulence and particle re-entrainment during the rather violent speed transients of the rotor fill/spin-up cycle.
Air backwashing of the cleanable filter should be done at least every time the oil is changed, but the more frequently it is done the better. Ideally, the entire process is automated and is done whenever the equipment is shut down for service, for example to refuel. In a further aspect, the cleaned and separated oil from the centrifuge can instead be returned to another tank or location, such as the fuel tank for burning with the fuel, as above noted.
While it is preferred that the noted storage container of the centrifuge be sized large enough to hold all of the contaminant that will be removed by the cleanable filter during the life of the equipment, this is not always feasible. In such cases, the centrifuge storage container is an easily removed and replaced modular component, facilitating easy periodic manual servicing, instead of the main filter. A disposable liner shell capsule extends along and lines the interior of the outer wall of the rotor and accumulates and contains contaminant, such that the centrifuge may be serviced by removing the outer sidewall of the rotor and then discarding the disposable liner shell capsule with contained contaminant therein and replacing same with another disposable liner shell capsule.
In a further aspect, a single centrifuge services multiple filters. Backwashable cleanable filters are connected in parallel to the centrifuge. The filters are cleaned sequentially, and the centrifuge is operated in sequential batch processing modes, one for each filter. Alternatively, if the storage capability of the centrifuge is large enough, it may handle the combined volumes of the filters at the same time.
In a desirable aspect, the invention provides a filtering system combining a cleanable filter and a centrifuge and transferring a contaminant storage function from the cleanable filter to the centrifuge.
In a further aspect, the invention provides a filtering system for filtering working fluid from a machine where filter capacity is too low for a permanent filter yet flow rate is too high for a centrifuge. The combination employs the flow rate capability of a filter with the storage capacity capability of a centrifuge.
In a further aspect, a simple effective centrifuge is provided.